"I'm not [the] referee. I didn't give [the] red card. But it was a clear red card - a two-footed tackle."
KOMPANY's FOUR-GAME BAN
(h) Carling Cup semi-final first leg
(a) Premier League
(h) Premier League
(a) Carling Cup semi-final second leg
Ferguson added: "They all appeal for players to get sent off. It's an unfortunate part of our game. What Wayne did was a natural reaction to a bad challenge."
Earlier, Manchester City manager Roberto Mancini had accused Rooney of putting pressure on Foy to send off Kompany. The defender, 25, faces a four-match ban after he was sent off for a tackle on Nani at Etihad Stadium.
Mancini said: "It was not a red card. Rooney told him [Foy] his decision."
City have appealed against the red card and a hearing will take place the day before Wednesday's game with Liverpool.
A three-man Football Association commission will decide if Foy made an "obvious error" in dismissing the Belgian.
If City are unsuccessful, the FA could extend the ban to five matches should it decide that the appeal had no chance of success, although that is thought unlikely in this case.
Mancini is confident his captain will be cleared by the FA, saying after the loss to United that "I am sure that we will win".
"There is no way Vincent shouldn't play against Liverpool in the Carling Cup semi-final on Wednesday. It was 300% not a sending off," the Italian added.
“It was a diabolical sending off and that was the turning point of the game. The person to blame is the referee. I know it was a two-footed challenge but it wasn't violent or malicious. It was a yellow card at the worst”
Former Manchester United manager Tommy Docherty on BBC Radio 5 Live
When asked to clarify if he felt Rooney had influenced the decision, Mancini stated: "Yes, he was near the referee."
Manchester United defender Rio Ferdinand defended the card.
He wrote on Twitter
: "How can there be any debate about the red card? You leave the ground with a two-foot tackle = Red card. Fact."
But former United midfielder Nicky Butt disagreed.
"When I first saw it, I thought it was a great tackle," Butt told BBC Radio 5 live. "I think it's the law that's wrong, not the referee. He [Kompany] clearly got the ball and didn't try to hurt the lad."
Kompany's 12th-minute dismissal came as part of a calamitous first half for City, in which United took a 3-0 lead.
But Mancini's side, who lead United by three points at the top of the Premier League, fought back in the second period and almost forced an unlikely third-round replay.
"My feeling is good because we gave such a good performance," added the Italian. "I am disappointed we lost but I'm happy with our performance and proud of my players.
"I am disappointed with this game but I think we took two steps forward. If we play this way against United with 10 men and with the same attitude and strength in every other game then I think we will win the title.
"We did not want to concede any more goals in the second half and did not give them any chances, which was very good.
"At this moment it is difficult because we have players injured, players away, and now I think it is incredible that Vincent cannot play against Liverpool [in the Carling Cup]."
The drama at the Etihad began before kick-off, when United named Paul Scholes on the bench after the veteran midfielder came out of retirement to sign for the Reds Devils until the end of the season.
Mancini admitted he was surprised to see the return of the 37-year-old. "Paul Scholes is a fantastic player but yes, it was strange to see him on the bench again," said the City boss.
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